On-site medical gas production plant and associated operating method

ABSTRACT

The invention relates to an on-site medical gas production plant ( 100 ) comprising a unit ( 50 ) for purifying gas, such as air, a first compartment (A) for storing purified gas, and a main gas line ( 10 ) fluidically connecting the gas purification unit ( 50 ) to the said first storage compartment (A). It furthermore comprises a three-way actuated valve (VA) arranged on the main gas line ( 10 ) upstream of the first storage compartment (A), and furthermore connected to the atmosphere (at  12 ) via a vent line ( 11 ), as well as an operating device ( 4 ) which controls at least the three-way actuated valve (VA), and at least a first gas analysis device (D 1 ) of which a first measurement line ( 29 ) is fluidically connected (at  28 ) to the main line ( 10 ), upstream of the three-way actuated valve (VA), and which is electrically connected to the said operating device ( 4 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/489,506 filed Sep. 18, 2014 which claims the benefit of priorityunder 35 U.S.C. §119 (a) and (b) to Canadian Patent Application No.2,829,065 filed Sep. 27, 2013, the entire contents of which areincorporated herein by reference.

BACKGROUND

The invention relates to a plant for medical air production on-site,that is to say in a hospital building or the like, employing a three-waysolenoid valve adapted to discharge product gas contaminated byimpurities to the atmosphere via a purge line connected to one of theports of the solenoid valve, and to a method for controlling oroperating such a plant.

The medical air used in hospitals, clinics, treatment centres, emergencyor incident units, or the like, for patients' respiration is amedicament whose composition is specified by the European Pharmacopoeia.

More precisely, medical air is ambient air compressed to a pressureabove atmospheric pressure, typically several bars, or to tens or evenhundreds of bars and containing (by volume) from 20.4% to 21.4% oxygen,at most 500 ppm CO₂, at most 5 ppm CO, at most 1 ppm SO₂, at most 2 ppmNO and NO₂, at most 67 ppm water and at most 0.1 mg/m³ oil; the oilvapours possibly present essentially come from the compression of theair.

It should be noted that, other than oxygen, the components mentionedabove (i.e. COx, NOx, water, or oil etc.) are in fact impurities whosepresence is tolerated within the limits of the Pharmacopoeia but whichideally are not present therein.

Medical air furthermore contains nitrogen, and may also contain othercompounds, such as argon.

Currently, medical air is delivered to hospitals or the like in threeforms, namely, depending on the case:

-   -   direct delivery in the form of compressed air, for example at an        absolute pressure of from 200 to 300 bar, in cylinders, that is        to say bottles or canisters of gas, or containers comprising a        plurality of bottles;    -   production on-site by mixing oxygen and nitrogen so as to create        nitrogen/oxygen mixtures, and    -   direct production on-site from ambient air treated, in        particular, by compressors and filtration/purification systems.

Of these, the production of air directly on-site by compressors andfiltration systems is the most widespread solution. Such a method isdescribed, for example, in the document EP-A-864818.

The ambient air is taken in and compressed by compressors to a pressurerange extending from 1 bar to 80 bar relative. This compressed air isthen filtered, that is to say purified, by means of one or moretreatment steps, for example by a set of filters and/or by employing apressure swing adsorption method (PSA).

The medical air produced in this way may be stored in one or moreintermediate buffer compartments, then sent through the network of pipeswhich passes through the hospital building in order to provision thetreatment rooms, bedrooms or the like with medical air. It is quiteclearly possible, and even indispensable in certain cases, to carry outintermediate expansion of the gas, for example in order to change from apressure of about 10 bar in the storage compartment to a pressure of 5or 8 bar in the network.

In general, any break in medical air provision is overcome by usingmedical air taken from a reserve or backup source in which the air iskept in gaseous form.

The other medical gases used in hospitals or treatment centres, such asoxygen, are also delivered in a similar way to the air. The compositionsof these other gases are also specified by the European or USPharmacopoeia.

Thus, oxygen may also be produced on-site by a PSA method by usingspecific adsorbents, such as lithium-exchanged zeolites X, making itpossible to retain the nitrogen contained in the air and thus producegaseous oxygen having a purity typically greater than 90%, or even 93%by volume, as is known from the document EP-A-297542.

However, the methods for producing medical air or other medical gasesused on-site (also referred to as on-site methods) present certaindrawbacks.

First, these methods do not permit easy monitoring of the reliability ofthe manufacturing process.

Thus, when an on-site medical air production unit is operatingautonomously, the manufacturing process is not overseen continuously andthe interventions on the plant take place on the basis of planning, thatis to say preventive maintenance, or when an error or a problem arisesin the plant, that is to say curative maintenance.

These interventions are therefore carried out independently of thestatus of the plant and its reliability, which is not optimal becausethey are carried out either too soon, and therefore without actual need,or too late, and therefore with an impact on the production process andpossibly on the final product.

Next, pollutant blockages in the main pipe occur when the gas producedis not compliant. This is because in existing plants, the controlsolenoid valve is a so called “2-way” solenoid valve which is arrangedon the main line.

Although it makes it possible to stop possible pollution upstream of thevalve, this pollution nevertheless remains blocked in the main line andnecessitates a total purge of the system upstream of the valve. This isnot ideal because it entails a shutdown of the gas production and manualintervention.

Furthermore, in the event of short-term breaks in the air provision due,for example, to temporary contamination at the inlet, the backup sourceis resorted to directly. However, this poses a problem because thebackup volume is limited and therefore, if the frequency of the breaksin provision is high, there is then a risk of draining the backupsource. In other words, it would be highly beneficial to be able toavoid this drawback by reducing the extent to which the backup source isused, so as to increase its autonomy over time.

Lastly, the air produced by the current methods and plants is in generalneither analyzed nor validated in pharmaceutical terms, which may raiseobvious problems of compliance and quality. Furthermore, when it isanalyzed, in the event of “noncompliance” this usually leads either toimmediate interruption of the production and changeover to a backupsource air, which may entail overuse of the backup air liable to cause apossible total break in the air provision, or to continuous provision ofnoncompliant air and parallel triggering of an alarm in order to warnthe user, who then needs to intervene manually. It will be understoodthat these solutions are not ideal either.

In summary, there is currently no method of validating air producedon-site which makes it possible to ensure that the air produced is infact compliant with the required specifications and which makes itpossible to ensure effective and reliable provision of medical air.

In other words, the problem which arises is to provide a plant forcontinuous on-site production of a medicament gas, particular medicalair, in accordance with good manufacturing practice (GMP) and a methodfor controlling or operating such a plant, which permit in particular:

-   -   supervision of the reliability of the manufacturing process with        rapid detection of any anomaly,    -   monitoring of the various production steps and in particular the        final production with, for each step, the possibility of a purge        thus making it possible to stop any contamination or        noncompliance of the gas produced, in particular medical air,        and/or    -   the use of the backup sources to be reduced to a minimal level.

SUMMARY

The solution of the invention is a plant for on-site production ofmedical gas, in particular medical-quality air, comprising:

-   -   a gas purification unit adapted to produce a purified gas from a        supply gas,    -   a first compartment for storing purified gas, and    -   a main gas line fluidically connecting the gas purification unit        to the said first storage compartment so as to supply the said        first storage compartment with purified gas coming from the gas        purification unit,

characterized in that it furthermore comprises:

-   -   a three-way actuated valve arranged on the main gas line between        the gas purification unit and the said first storage        compartment, and furthermore connected to the atmosphere via a        vent line,    -   an operating device which controls at least one three-way        actuated valve,    -   at least a first gas analysis device of which a first        measurement line is fluidically connected to the main line,        upstream of the three-way actuated valve,

and which is electrically connected to the said operating device, and inwhich the operating device is designed and adapted to act on thethree-way actuated valve in response to a signal received from the gasanalysis device, so as to allow the gas present in the main pipe to passto the vent line when the signal received from the gas analysis devicecorresponds to a “contamination” signal of the main pipe, andsimultaneously to prevent any gas being sent to the said first storagecompartment.

Depending on the case, the plant of the invention may comprise one ormore of the following technical characteristics:

-   -   the gas compression unit supplies the gas purification unit with        a gas to be purified, compressed to a pressure higher than 1 bar        absolute.    -   the gas compression unit supplies the gas purification unit with        compressed ambient air.    -   the gas compression unit comprises at least one screw, piston,        scroll or diaphragm compressor.    -   the gas compression unit comprises a plurality of compressors,        in particular arranged in parallel.    -   the gas purification unit comprises at least one adsorber, each        containing at least one bed of at least one adsorbent material,        preferably at least 2 adsorbers arranged in parallel.    -   the gas purification unit comprises at least one adsorber        operating in a cycle of the PSA type.    -   the gas purification unit comprises at least two adsorbers        operating alternately, and the operating device is designed and        adapted to act on the gas purification unit and/or the gas        compression unit so as to stop any production of gas by the        adsorber which was in operation at the time when the gas        analysis device transmitted the “contamination” signal of the        main pipe to the operating device.    -   the “contamination” signal corresponds to a given level of at        least one impurity, in particular one or more impurities        selected from water vapour, or oil vapours, SOx, COx and/or NOx.    -   the “contamination” signal corresponds to a preset threshold        level, for example corresponding to a maximum level set by the        United States or European Pharmacopoeia as regards the        aforementioned impurities (i.e. water and oil vapour, SOx, COx        and/or NOx) or a maximum limit value lower than the said        corrected maximum values (for example 80% or 90% of the maximum        value in the Pharmacopoeia), which makes it possible to ensure        an operational safety margin.    -   the operating device is designed and adapted to act on the (two        or three-way) actuated valve(s) in response to a signal received        from the gas analysis device, so as to stop any gas present in        the main pipe from passing to the vent line when the signal        received from the gas analysis device corresponds to a        “compliant gas” signal of the main pipe, and simultaneously to        allow gas to be sent to the said first storage compartment.    -   the gas purification unit furthermore comprises one or more        filters.    -   the gas purification unit, in particular the adsorbers, makes it        possible to eliminate all or some of the impurities which are        possibly present in the ambient air to be purified or which have        been introduced therein during the compression, in particular        water vapour, oil vapours, SOx, COx and/or NOx, so as to produce        a medical gas compliant with the Pharmacopoeia, in particular        medical air compliant with the European Pharmacopoeia. The        adsorbers may include desiccants and/or deliquescent dryers.        Alternatives to adsorber based systems are refrigerant dryers or        membrane dryers. Generally any suitable device for dehumidifying        the air is compatible with the device and system described        herein.    -   the valve is a 3-way actuated valve, of which one of the ports        is fluidically connected via a vent line to the atmosphere and        the other two ports are fluidically connected to the main line.    -   the valve is an actuated valve controlled by an operating unit,        preferably the operating unit electrically connected to the        three-way actuated valve.    -   The gas compression unit comprises one (or more) gas inlets        supplied with atmospheric air.    -   the main line connects the first compartment for storing        purified gas to at least one gas consumer site, preferably a        network of pipes in a hospital building    -   the main gas line comprises a second compartment for storing        purified gas, located between the first storage compartment and        the said at least one gas consumer site. The first and second        compartments are therefore arranged in series on the main line.    -   the main gas line branches downstream of the first storage        compartment into a secondary line fluidically connected upstream        to the said main line and downstream to at least one gas        consumer site, that is to say directly or indirectly, for        example by being connected to the main gas line, the said        secondary gas line comprising a third compartment for storing        purified gas. The first and third compartments are therefore        also arranged in series, whereas the second and third        compartments are arranged in parallel on the main line and the        secondary line, respectively.    -   it furthermore comprises a backup line fluidically connecting a        backup source, such as a reserve or store of medical air, to the        said at least one gas consumer site, either directly or        indirectly by being connected to the main gas line or the said        secondary line.    -   it furthermore comprises at least 2-way actuated valves are        typically 2-way actuated valves, arranged on the main line or        the secondary line, with a first actuated valve arranged between        the first compartment and the second compartment for storing        purified gas, and a second actuated valve arranged between the        first compartment and the third compartment for storing purified        gas,    -   it furthermore comprises at least two-way actuated valves,        arranged on the main line and the secondary line, with a third        actuated valve arranged downstream of the second compartment        and/or a fourth actuated valve arranged downstream of the third        compartment,    -   it furthermore comprises a first purge line, fluidically        connected upstream to the main line and downstream to the vent        line, the first purge line preferably being fluidically        connected to the main line downstream of the second compartment.    -   it furthermore comprises a second purge line fluidically        connected upstream to the secondary line and downstream to the        vent line, the second purge line preferably being fluidically        connected to the secondary line downstream of the third        compartment.    -   the first purge line comprises a fifth actuated valve and/or the        second purge line comprises a sixth actuated valve.    -   it comprises at least a first gas analysis device, the first        measurement line of which is fluidically connected to the main        line, upstream of the three-way actuated valve,    -   it comprises a second gas analysis device, of which at least one        second measurement line is fluidically connected to the main        line and/or to the secondary line.    -   the second measurement line comprises a seventh and/or an eighth        actuated valve.    -   the operating unit furthermore controls the gas purification        unit, the gas compression unit, one or more of the actuated        valves and the gas analysis device or devices.    -   it comprises one or more nonreturn valves arranged on all or        some of the pipes or lines conveying the gas.

The invention also relates to a method for operating an on-site medicalgas production plant, in particular a plant according to the inventionas described above, comprising the steps of:

a) producing a purified gas from a supply gas, in particular atmosphericair compressed to a pressure greater than atmospheric pressure (i.e. >1atm),

b) transporting the purified gas obtained in step a) by means of a maingas pipe,

c) storing at least a part of the purified gas in a first compartmentthe storing the gas supplied by the gas pipe,

characterized in that it furthermore comprises the steps of:

d) determining in the main gas pipe, upstream of the first storagecompartment, an impurity level of at least one given impurity in the gasproduced in step a), and

e) controlling a three-way actuated valve arranged on the main gas lineupstream of the first storage compartment, and furthermore connected tothe atmosphere via a vent line, so as to divert the gas present in themain pipe, upstream of the three-way actuated valve, to the vent linewhen the impurity level measured in step d) is greater than or equal toa preset threshold level.

Depending on the case, the method of the invention may comprise one ormore of the following technical characteristics:

-   -   in step e), the gas present in the main pipe, upstream of the        three-way actuated valve, is diverted to the vent line and gas        is simultaneously stopped from being sent to the first storage        compartment, when the impurity level measured in step d) is        greater than or equal to a preset threshold level.    -   in step a), a purified gas is produced from a supply gas treated        in a gas purification unit comprising at least two adsorbers        operating alternately, and when an impurity level greater than        or equal to a preset threshold level is determined in the gas        produced by one of the said adsorbers, the production of the gas        by the said adsorber is stopped and the production of gas by the        other or another of the said adsorbers is started.    -   gaseous flushing of the main pipe part containing an impurity        level greater than or equal to the preset threshold level with        purified gas is carried out and the gas flow thus generated is        discharged to the atmosphere via the vent line.    -   the gas to be purified is ambient air and the purified gas is        medical air or medical oxygen, that is to say with the        specifications of the European Pharmacopoeia, as explained        above.    -   the impurity or impurities are selected from NOx, SOx, COx,        water vapour and hydrocarbon vapours, in particular oil vapours.    -   the medical air produced contains (by volume) from 20.4% to        21.4% oxygen, at most 500 ppm CO₂, at most 5 ppm CO, at most 1        ppm SO₂, at most 2 ppm NO and NO₂, at most 67 ppm water, at most        0.1 mg/m³ oil, and nitrogen.    -   in step d), a gas analysis device is used in order to determine        the impurity level in the main gas pipe.    -   in step e), an operating device, such as a programmable        automaton, is used in order to control the three-way actuated        valve, the said operating device acting in response to the        measurements taken by the gas analysis device.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the nature and objects for the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawing, inwhich like elements are given the same or analogous reference numbersand wherein:

FIG. 1, which represents the block diagram of an embodiment of a plant100 for on-site production of medical gases, controlled by the operatingmethod according to the invention, which plant 100 is connected to thenetwork of pipes 30 of a hospital building.

FIG. 2 illustrates and alternative arrangement of the invention having asingle storage compartment A.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described in more detail withreference to the appended FIGS. 1 and 2, which represent the blockdiagram of an embodiment of a plant 100 for on-site production ofmedical gases, controlled by the operating method according to theinvention, which plant 100 is connected to the network of pipes 30 of ahospital building or the like.

The gas produced here is medical air, that is to say purified airsatisfying the specifications of the European Pharmacopoeia mentionedabove. Nevertheless, such a plant 100 may be used for manufacturingother medical gases, for example medical oxygen from ambient air.

More precisely, in the embodiment illustrated in FIG. 1, the on-sitemedical air production plant 100 comprises a gas purification unit 50supplied by a gas compression unit 31, that is to say one or more aircompressors taking in ambient air at atmospheric pressure (i.e. 1 atm)through their supply inlet 32 and delivering compressed air at apressure higher than atmospheric pressure, for example at a pressure ofbetween 1 bar and 80 bar absolute. This compressor or these compressors31 may be one or more screw, piston, scroll or diaphragm compressors.

The compressed air supplies the gas purification unit 50, which herecomprises two adsorbers 1, 2 operating in parallel according to cyclesof the PSA type (Pressure Swing Adsorption) or TSA type (TemperatureSwing Adsorption), that is to say one is in production phase while theother is in regeneration phase, and vice versa. Typically, the durationof a production cycle is between 1 and 30 minutes, approximately,preferably from less than 10 to 15 minutes.

These adsorbers each contain at least one bed of at least one adsorbentmaterial, for example adsorbent materials such as zeolites, aluminas,active carbon, silica gel or any other molecular sieve capable ofstopping the impurities present in ambient air.

Depending on the embodiment in question, the gas purification unit 50may also comprise a single adsorber or more than 2 adsorbers 1, 2, forexample at least 3 adsorbers.

These types of adsorbers 1, 2 and PSA or TSA cycle are well known and,in this regard, reference may furthermore be made for example to thedocuments EP-A-716274, EP-A-718024, EP-A-922482, GB-A-1551348,EP-A-930089.

In all cases, the adsorbers 1, 2 make it possible to eliminate all orsome of the impurities which are possibly present in the ambient air tobe purified or which have been introduced therein during the compression(at 31), in particular water vapour, oil vapours, SOx, COx and/or NOx,so as to produce a medical gas compliant with the Pharmacopoeia, inparticular medical air compliant with the European Pharmacopoeia.

Next, the purified air (or any other medical gas) produced by the gaspurification unit 50 is recovered in outlet conduits 9 which supply amain line 10 conveying gas, that is to say a pipe or a tube deliveringgas, which is adapted and designed to convey the purified air producedin this way to a first storage compartment A, that is defined as abuffer gas volume container such as a vessel, tank or discrete sectionof pipe in which the purified medical air can be stored and/orhomogenized before being sent to one or more consumer sites 30, such asa network of gas pipes passing through a hospital building in order toconvey the medical air to the various rooms in which it is to be used,such as treatment rooms, emergency rooms, recovery rooms, bedrooms orany other any other location.

Preferably the storage compartment A is in unidirectional fluidcommunication with the gas purification unit 50 via main line 10 suchthat gas entering the storage compartment A cannot return upstreamtoward the gas purification unit 50.

The main gas line 10 therefore fluidically connects the outlet (oroutlets) 9 of the gas purification unit 50 to the said first storagecompartment A so as to supply it with purified air coming from the twoadsorbers 1, 2 of the gas purification unit 50.

The operation of the compressor or the compressors 31 and thepurification cycles taking place in the gas purification unit 50 arecontrolled and monitored by an operating device 4, for example aprogrammable automaton or the like, connected to the gas purificationunit 50 by electrical connections 8, such as electrical cables.

It should, however, be noted that communication between the variouselements and devices of the plant, in particular with the automaton 4,could in general also take place via wireless links, for example via oneor more wireless transmitter devices or systems such as radiofrequency(RF), Bluetooth, Zigbee, wifi, GSM or GPRS, and one or more receiverantennas for carrying out wireless transmissions of data adapted to thetype of transmitter used.

Preferably, the automaton 4 or the like is programmed according to therequirements of the hospital site in question and can be reprogrammed ifthe requirements of the site change, for example.

In order to regulate and monitor the conveyance of gas in the main gasline 10, an actuated valve VA is arranged on the said main line 10between the gas purification unit 50 and the first storage compartmentA. The actuated valve VA is also controlled by the operating device 4via an electrical connection 5, such as an electrical cable.

According to one preferred embodiment shown in FIG. 1, the valve VA is athree-way actuated valve such as a solenoid valve, one of the ports ofwhich is fluidically connected via a vent line 11 to the ambientatmosphere (at 12) where there is preferably a device for venting to theatmosphere, such as a vent valve (not represented), and the other twoports of which are fluidically connected to the main line 10.

The air produced by the gas purification unit 50 therefore passesthrough two of the ports of the actuated valve VA, that is to say thefirst and second ports of the actuated valve VA, when it passes normallythrough the said actuated valve VA in the direction of the buffercompartment A where the purified gas can be stored.

Conversely, in the event of contamination of the line 10 upstream of thevalve VA, this pollution can be expelled easily and effectively from thecontaminated conduit portion of the main line 10, without the need for atotal purge of the system upstream of the valve VA.

This is done conventionally by flushing the conduit portion polluted byimpurities with pure air produced by the gas purification unit 50. Thegas flow entraining the impurities is then discharged via the third portof the actuated valve VA to the atmosphere, through the vent line 11 tothe ambient atmosphere. In other words, the air produced by the gaspurification unit 1, 2 will then entrain the pollutants with it andthese will be disposed of to the atmosphere (at 12).

The 3-way actuated valve VA therefore makes it possible not only toblock any possible pollution on the main line 10 in order to confine itupstream of the actuated valve VA, but also subsequently to dischargethis pollution of the main line 10 to the outside (at 12) and thus topurge the main line 10 upstream of the valve VA.

This solution makes it possible to avoid shutting down the productionprocess entirely and resorting to the backup 3, that is to say a reserveof pure gas, in the event of temporary pollution of the air taken in orcreated by the production line.

Furthermore, the first buffer compartment A makes it possible to takeover the delivery of the purified gas, such as medical air, when thevalve VA is in the vent position, that is to say when a purge of theline 10 is ongoing, so as here again to reduce the frequency of use ofthe backup source 3.

The first compartment A also makes it possible to protect the productionunit 50 from consumption peaks, that is to say peaks in demand from theconsumer sites 30, and to homogenize the air produced by the productionunit.

The monitoring of the composition of the gas produced, such as purifiedair, delivered by the production unit 50 is carried out by means of afirst gas analysis device D1, such as an analysis cabinet or any othersuitable gas analyzer, the measurement line 29 of which is connectedfluidically (at 28) to the main line 10, upstream of the 3-way actuatedvalve VA.

This gas analysis device D1 is connected to the operating device 4 viaan electrical connection 7, such as an electrical cable or the like, soas to transmit measurement signals and optionally other informationthereto.

As a function of the signals received, the operating device 4 canretroact on the 3-way actuated valve VA and preferably the otherelements of the plant, such as production unit 50, compressor 31, etc.,in order to trigger a purge of the line 10 when pollution is detected.

More precisely, in order to evaluate the reliability of the method andof the production plant, the quality of the air produced is analyzedusing the analysis cabinet D1, in particular the levels of O₂, H₂O, CO₂and oil vapour. Complementary monitoring variables (for exampletemperature, pressure, vibrations, etc.) are furthermore collected fromthe plant.

The analysis results as well as the monitoring variables may also thenbe optionally processed by the operating device 4, such as an automaton,on the basis of statistical process control (SPC) in order to define thereliability of the production process.

The processing of the data is carried out for each of the productionlines, that is to say for each of the adsorbers 1, 2 of the productionunit 50 as well as the compressors 31, on the basis of conventionalcontrol elements, such as aptitude indicators of the production process,control chart of the variables, average, control limits, trend analysisof the variables, etc.

On the basis of the results and the predefined parameters, it is thenpossible to determine whether or not the manufacturing process isreliable.

Thus, when the operating device 4 determines that the level of one ormore impurities in the main gas pipe 10, in particular upstream of thefirst storage compartment A, is greater than or equal to a presetthreshold level, for example the maximum values set by the EuropeanPharmacopoeia as regards the level of water vapour, or oil vapours, SOx,COx and/or NOx, the said operating device 4 controls the three-wayactuated valve VA so as to divert the gas present in the main pipe 10,in particular the gas present upstream of the three-way actuated valveVA, to the vent line 11 and thus purge the main line 10 of the impure,that is to say noncompliant, the gas contained therein.

In this case, i.e. when the manufacturing process is not reliable, or nolonger reliable, the production line in question, that is to say theadsorbers 1 or 2 and the associated compressor 31, is shut down and thesecond line takes over for producing purified air, while the other lineis regenerated, reinitialized and/or undergoes a maintenance operation.

In other words, in the event of excessive impurity levels, the gaspresent in the main pipe 10 is diverted to the vent line 11 and gas issimultaneously stopped being sent to the first storage compartment A.

At this time, the production of the gas by the adsorber 1 or 2 inquestion is stopped and production of gas by the other adsorber 1 or 2,respectively, of the production unit 50 is started.

This gas produced by the other adsorber will then be used to carry outgaseous flushing of the part of the main pipe 10 containing the impuritylevel greater than or equal to the preset threshold level then willsubsequently be discharged to the atmosphere as a result of the gas flowthus generated, via the vent line 11.

When the pipe 10 has been purged and the impurity level has returned tonormal, the operating device 4 will control the 3-way actuated valve VAin order to stop the purge and allow gas again to be sent to thecompartments A, B and/or C located downstream.

The gas produced in this way is then subjected to monitoring as before.In the event of unreliability of the second line as well, the systemthen switches to the backup source 3. Specifically, the plant alsocomprises a backup line 40 fluidically connecting a backup source 3,such as a backup reservoir containing medical air, to the gas consumersites 30, directly or indirectly, that is to say by being connected at23 to the main gas line 10 or to a secondary line 20.

The secondary line 20 is in fact another gas line arranged in parallelwith the main line 10 and used as an alternative passage for the gascoming from the compartment A, for example, and/or from the productionunit 50, when the main line 10 is out of use, for example contaminatedand/or undergoing a maintenance operation.

In other words, the main gas line 10 branches (at 21) downstream of thefirst compartment A into a secondary line 20. The latter 20 is thereforefluidically connected on its upstream side (at 21) to the said main line10 and, by its downstream end, to at least one gas consumer site (30),directly or indirectly, that is to say by being connected (at 22) to themain gas line 10.

Furthermore line 10 also comprises a second buffer compartment B forstoring purified gas, located between the first compartment A and thegas consumer site or sites, such as a network of pipes 30 of a hospitalbuilding, and the secondary line 20 in turn comprises a thirdcompartment C for storing purified gas.

The compartments B, C are used to supply the consumer site or sites 30with respiratory gas. In fact, the compartments B and C are used toprovide medical air in alternation, that is to say while one compartment(for example B) is being filled or analyzed for compliance, the second(respectively C) delivers the gas to the hospital network 30, or viceversa.

In general, maintenance of the plant 100 is triggered by the automaton 4on an anticipatory basis when the production parameters of one or bothproduction units 1, 2 reach a predetermined threshold.

It will furthermore be noted that 2-way actuated valves are arranged onthe main line 10 and the secondary line 20. More precisely, a firstactuated valve V1 is arranged between the first compartment A and thesecond compartment B, and a second actuated valve V3 is arranged betweenthe first compartment A and the third compartment C for storing purifiedgas.

Furthermore, a third actuated valve V2 is arranged downstream of thesecond compartment B and a fourth actuated valve V4 is arrangeddownstream of the third compartment C. These 2-way actuated valves arecontrolled by the operating device 4 via electrical connections 6, 37,such as cables or the like, and make it possible to control the passageof the gas through the lines 10 and 20 and therefore to divide the pipes10, 20 into well-determined sections, and also to manage and/or operatethe gas inlets and/or outlets of the compartments B and C.

The plant 100 furthermore comprises a first purge line 13 fluidicallyconnected by its upstream end 24 to the main line 10, preferablydownstream of the second compartment B, and by its downstream end 25 tothe vent line 11, as well as a second purge line 14 fluidicallyconnected by its upstream end 26 to the secondary line 20, preferablydownstream of the third compartment C, and by its downstream end 27 tothe vent line 11.

The first purge line 13 comprises a fifth actuated valve V7 and thesecond purge line 14 comprises a sixth actuated valve V8 used to controlthe passage of the gas to the vent line 11. The operating device 4 alsocontrols the actuated valves V7, V8 via electrical connections 37.

These purge lines 13, 14 make it possible to purge the portions of lines10, 20 as well as the compartments B and C, respectively, locatedupstream of the actuated valves V2 and V4, respectively.

A second gas analysis device D2, such as an analysis cabinet or thelike, is provided and includes at least one second measurement line 36,branching into two subsections 36 a, 36 b, which is fluidicallyconnected (at 34, 35) to the main line 10 and to the secondary line 20,in particular by means of the subsections 36 a, 36 b. Preferably, thesecond measurement line 36, 36 a, 36 b comprises a seventh V5 and/or aneighth V6 actuated valve.

This second gas analysis device D2 makes it possible to determine thecomposition of the gas circulating in the main 10 and secondary 20lines, downstream of the compartments B, C, that is to say it makes itpossible to analyze discontinuously the gas taken from the compartmentsB and C. As before, this second gas analysis device D2 cooperates withthe operating device 4, which itself controls the actuated valves V5, V6via electrical connections 37. The electrical supply of the plant 100 iscarried out conventionally by current from the mains, for example at avoltage of between 1 and 600 V, typically 24 V, 230 V or 400 V.

If need be, measurement means (not shown) may be provided in order todetermine the pressure of the medical air contained in the compartmentsA, B, C for storage and homogenization of the gas and optionallyretroact via the operating device 4 on the compression unit 31 and/orthe production unit 50 so as to regulate the production of the gas, suchas air, by taking into account the pressure (or pressures) thusmeasured. For example, the operating means 4 may be programmed in orderto cause shutdown of the flow source 31 and/or triggering of an audioand/or visual alarm, when a pressure sensor arranged at the buffercompartment A detects a pressure or a pressure difference greater thanor, conversely, less than a preset threshold value. This type ofpressure regulation is well known and will not be described in detailhere.

Furthermore, in order to ensure even more effective purification of theair taken in by the compressor 31, one (or more) mechanical filtrationdevices (not represented in detail) may be provided, arranged at one ormore sites between the air source 31 and the hospital network 30. Forexample, the compression unit may comprise one or more filters at theinlet 32 and/or outlet 33 in order to retain the dust contained in theambient air and the condensates due to the compression, for examplecyclone filters or separators, micron filters or the like.

FIG. 2 illustrates and alternative arrangement of the invention having asingle storage compartment A. The basic elements are the same as FIG. 1,namely the medical air production unit 50 fed by compressor 31 directingmedical via main line 10 to a point of use 30 such as a hospital pipingnetwork. Storage compartment A in this example is a discrete section ofpipe which is fluidically isolated from the preceding main line 10 suchas by a one way check valve. In FIG. 2, each valve VA, VB and 110 mayall be two way actuated valves under a common operating device 4 control200 or one or more may be also, or exclusively manually operated. In onepreferred embodiment, VA and VB are under operating device 4 control200, but bypass valve 110 is a manual only valve. FIG. 2's designincludes a backup medical air supply 140 which may be a tank or cylinderof medical air.

Medical air production unit 50 may, instead of being the airpurification systems of FIGS. 1 and 2, be a synthetic air productionsystem wherein oxygen and nitrogen gases are blended to form arespiratory gas substitute for air (synthetic air). The nitrogen andoxygen can be medical grade gases or can be purified to medical gradestandards pre- or post-blending using an air purification system such asthose described in FIGS. 1 and 2. The nitrogen and oxygen sources may befor example bulk storage tanks of cryogenic liquids that are vaporizedand temperature adjusted pre- or post-blending. Other sources of gasesfor the synthetic air could include direct pipelines from an AirSeparation plant or other means for storing or delivering the nitrogenand oxygen to the medical air production unit 50.

In general, the plant 100 of the invention for production of medical airon-site, that is to say in a hospital building or the like, thereforeemploys a three-way actuated valve adapted to discharge product gascontaminated by impurities to the atmosphere via a purge line connectedto one of the ports of the actuated valve VA, in response to detectionof the said contamination by an analysis device D1 cooperating with theoperating device 4.

The medical air production plant 100 of the invention may be useddirectly on the site where the gas is used, that is to say directly in ahospital building or the like. It may therefore be installed directly ina room of the hospital building or outside the said building or incontainers, and connected to the network 30 of pipes conveying the gasinside the building.

While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications, and variations as fallwithin the spirit and broad scope of the appended claims. The presentinvention may suitably comprise, consist or consist essentially of theelements disclosed and may be practiced in the absence of an element notdisclosed. Furthermore, if there is language referring to order, such asfirst and second, it should be understood in an exemplary sense and notin a limiting sense. For example, it can be recognized by those skilledin the art that certain steps can be combined into a single step.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means thesubsequently identified claim elements are a nonexclusive listing (i.e.,anything else may be additionally included and remain within the scopeof “comprising”). “Comprising” as used herein may be replaced by themore limited transitional terms “consisting essentially of” and“consisting of” unless otherwise indicated herein.

“Providing” in a claim is defined to mean furnishing, supplying, makingavailable, or preparing something. The step may be performed by anyactor in the absence of express language in the claim to the contrary.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

All references identified herein are each hereby incorporated byreference into this application in their entireties, as well as for thespecific information for which each is cited.

What is claimed is:
 1. A method for operating an on-site medical gasproduction plant (100), the plant comprising: a synthetic air productionunit (50) configured to produce a mixture comprising nitrogen and oxygenwhich is medically suitable for respiration by patients in place of orin addition to air, a first compartment (A) for storing the purifiedgas, and a main gas line (10) fluidically connecting the synthetic airproduction unit (50) to the first storage compartment (A) so as tosupply the said first storage compartment (A) with the synthetic aircoming from the synthetic air production unit (50), wherein the main gasline furthermore comprises: a actuated valve (VA) arranged on the maingas line (10) between the synthetic air production unit (50) and thefirst storage compartment (A), and furthermore connected to theatmosphere (at 12) via a vent line (11), an operating device (4) whichcontrols at least one actuated valve (VA), at least a first gas analysisdevice (D1) of which a first measurement line (29) is fluidicallyconnected (at 28) to the main line (10), upstream of the actuated valve(VA), and which is electrically connected to the operating device (4),and in which the operating device (4) is designed and adapted to act onthe actuated valve (VA) in response to a signal received from the gasanalysis device (D1), so as to divert a gas present in the main pipe(10) to pass to the vent line (11) when the signal received from the gasanalysis device (D1) corresponds to a contamination signal based on ananalysis of the gas in the main pipe (10), and simultaneously to preventthe gas present in the main pipe (10) from being sent to the said firststorage compartment (A); the method comprising the steps of: a)producing a synthetic air comprising nitrogen and oxygen which ismedically suitable for respiration by patients in place of or inaddition to air, b) transporting the synthetic air obtained in step a)in a main gas pipe (10), c) storing at least a part of the synthetic airin a first compartment (A) for storing gas supplied by the main gas pipe(10), d) determining in the main gas pipe (10), upstream of the firststorage compartment (A), an impurity level of at least one givenimpurity in the synthetic air produced in step a), and e) controlling aactuated valve (VA) arranged on the main gas line (10) upstream of thefirst storage compartment (A), and furthermore connected to theatmosphere (at 12) via a vent line (11), so as to divert the syntheticair present in the main pipe (10), upstream of the actuated valve (VA),to the vent line (11) when the impurity level measured in step d) isgreater than or equal to a preset threshold level.
 2. The methodaccording to claim 1, wherein in step e), the synthetic air present inthe main pipe (10), upstream of the actuated valve (VA), is diverted tothe vent line (11) and synthetic air is simultaneously stopped frombeing sent to the first storage compartment (A), when the impurity levelmeasured in step d) is greater than or equal to a preset thresholdlevel.
 3. The method according to claim 2, wherein: in step a), thesynthetic air production unit (50) comprises at least two adsorbers (1,2) operating alternately, and when an impurity level greater than orequal to a preset threshold level is determined in the gas produced byone of the adsorbers, the production of the gas by the adsorber isstopped and the production of purified gas by another of the adsorber(s)is started.
 4. The method according to claim 2, wherein a gaseousflushing step of the main pipe (10) containing an impurity level greaterthan or equal to the preset threshold level with synthetic air iscarried out and the gas flow thus generated is discharged to theatmosphere via the vent line (11).
 5. The method of claim 1, wherein thenitrogen and/or oxygen are from a less pure supply gas source to bepurified by the synthetic air production unit (50) to yield a syntheticair that qualifies as is a medical air or a medical oxygen gas.
 6. Themethod of claim 5, wherein the synthetic medical air meets the followingcriteria: 19.5% to 23.5% oxygen, with predominant balance nitrogenCarbon monoxide: <10 ppm Carbon dioxide: <500 ppm Nitrogen dioxide: <2.5ppm Nitric oxide: <2.5 ppm Sulfur dioxide: <5 ppm.
 7. The method ofclaim 1, wherein the impurity or impurities are selected from NOx, SOx,COx, water vapour, hydrocarbon vapours, or combinations thereof.
 8. Themethod of claim 5, wherein the medical air produced contains (by volume)from 20.4% to 21.4% oxygen, at most 500 ppm CO₂, at most 5 ppm CO, atmost 1 ppm SO₂, at most 2 ppm NO and NO₂, at most 67 ppm water, at most0.1 mg/m³ oil, and nitrogen.
 9. The method of claim 5, wherein in stepd), a gas analysis device (D1) determines the impurity level in the gasin the main gas pipe (10).
 10. The method of claim 9, wherein in stepe), an operating device (4) controls the actuated valve (VA), theoperating device (4) acting in response to the measurements taken by thegas analysis device (D1).
 11. The method of claim 10, wherein theoperating device (4) monitors the signal received (210) from the gasanalysis device (D1) during a first defined period of a purge operationto determine if the contamination signal persists for longer than aspecified period of time and wherein, if the contamination signalpersists for less than the specified period, the operating device (4)closes the vent line (11) actuated valve (VB) to end the purge operationand reopens the main line (10) actuated valve (VA) to resume delivery ofgas from the gas purification unit (50) to the first storage compartment(A).